Case 02 - Asthma Flashcards
Percentage of the population affected asthma
5-8%
Asthma is characterised by…
…recurrent episodes of SOB, cough and wheeze caused by reversible airways obstruction.
Another word for shortness of breath
Dyspnoea
What 3 factors contribute to airway narrowing in asthma and what is their cause?
- Bronchial muscle contraction (triggered by a variety of stimuli)
- Mucosal swelling/inflammation (mast cell and basophil degranulation –> release of inflammatory mediators)
- Increased mucus production
Symptoms
Intermittent dyspnoea, wheeze, cough, chest tightness, sputum
Which symptom is often nocturnal?
Cough
Precipitants (triggers/exacerbators)
Cold air, exercise, emotion, allergens, infection, smoking (inc. passive), NSAIDs, beta-blockers
What is meant by diurnal variation
Symptoms and/or peak flow may vary over the day and are typically worse in the morning (known as morning ‘dips’)
What 3 questions can be asked to asses symptomatic control?
(1) In the last week/month, have you had any difficulties sleeping due to your asthma symptoms (inc. cough and breathlessness)?
(2) Have you had your usual asthma symptoms (e.g. cough, wheeze, chest tightness or breathlessness) during the day?
(3) Has your asthma interfered with your usual daily activities (e.g. school, work, housework)?
An unexpected condition many (40-60%) asthmatics have
Acid reflux
Why treating acid reflux in asthma patients is beneficial
Improves spirometry (but not symptoms!)
Conditions atopic individuals typically have aside from asthma
Eczema, hay fever, allergies
Allergens that commonly trigger asthma
House dust mites, pollen, fur
Percentage of asthma cases that are occupational
15%
Telling sign asthma may be occupational
Remission of symptoms during weekends or holidays
What to do if you suspect occupational asthma
Ask the patient to measure their peak flow at home and at work, at the same time intervals
Signs
- General overview: audible wheeze, cough
- Arms: tachypnoea
- Auscultation: reduced airy entry (decreased breath sounds), widespread polyphonic wheeze
- Percussion: hyper-resonance
Signs of a severe asthma attack
- Inability to complete sentences
- Pulse >110 bpm
- RR >25/min
- PEFR 33-50% predicted
Signs of a life-threatening asthma attack
- Silent chest
- Confusion, exhaustion
- Cyanosis
- Low PaO2 (<8 kPa, i.e. rasp failure), but normal PaCO2 (4.7-6.0 kPa) - dangerous in this case!
- Low O2 sats / SpO2 (<92%)
- Bradycardia (<60 bpm)
- PEFR <33% predicted
Sign that indicates near fatal asthma and what should be done
A rising pCO2! Initially pCO2 is low due to hyperventilation. If it becomes normal or raised, this indicates failing respiratory effort and the patient needs ventilation!
What to do if you suspect asthma in an adult
Perform spirometry or, if not available, peak flow
FEV1/FVC <0.7 –> high probability of asthma, >0.7 –> low probability
High probability of asthma –> trial of asthma treatment
- If successful, continue minimum effective dose
- If unsuccessful, assess inhaler technique/compliance –> if no further improvement consider onward referral
Low probability of asthma –> investigate/treat other cause
- If no response to treatment, consider further investigation or onward referral
What to do if you suspect asthma in a child
Same as for adults, except don’t perform spirometry or PEFR
Tests for chronic asthma
- PEFR monitoring (diurnal variation of >20% on ≥3 days/week for 2 weeks)
- Spirometry (decreased FEV1/FVC,
(Diagnostic) tests for chronic asthma
- PEFR monitoring (diurnal variation of >20% on ≥3 days/week for 2 weeks)
- Spirometry (decreased FEV1/FVC, increased RV)
- ≥15% improvement in FEV1 following a trial of B2 agonists or steroids
- CXR (hyperinflation)
- Skin-prick tests to help identify allergens
- Histamine or methacholine challenge (airway hyper-reponsiveness is characteristic of asthma - patients with asthma only need very low doses of methacholine or histamine for a 20% fall in FEV1)
- Aspergillus serology (why?)
O2 sats of (1) are a serious sign (check ABGs!), except for individuals with what (2)?
(1) <92%
2) COPD (target SpO2: 88-92%
O2 sats of (1) are a serious sign (check ABGs!), except for individuals with what (2)?
(1) <92%
2) COPD (target SpO2: 88-92%
FEV1, FVC and FEV1/FVC ratio for
(1) normal airways
(2) obstructive lung disease
(3) restrictive lung disease
(1) FEV1 >80% predicted, FVC >80% predicted, FEV1/FVC 75-80% predicted
(2) FEV1 <80% predicted, FVC normal or low, FEV1/FVC <70% predicted
(3) FEV1 <80% predicted, FVC <80% predicted, FEV1/FVC >70% predicted
FEV1, FVC and FEV1/FVC ratio for
(1) normal airways
(2) obstructive lung disease
(3) restrictive lung disease
(1) FEV1 >80% predicted, FVC >80% predicted, FEV1/FVC 75-80% predicted
(2) FEV1 <80% predicted, FVC normal or low, FEV1/FVC <70% predicted
(3) FEV1 <80% predicted, FVC <80% predicted, FEV1/FVC >70% predicted
Some restrictive lung diseases
Fibrosis, pleural effusion (see Oxford Handbook)
TLC and RV in
(1) obstructive lung disease
(2) restrictive lung disease
(1) Increased (hyperinflation)
(2) Reduced
Differentials
- Pulmonary oedema (‘cardiac asthma’, ?)
- COPD (may co-exist)
- Large airway obstruction (e.g. foreign body, tumour)
- SVC obstruction (wheeze/dyspnoea not episodic, ?)
- Pneumothorax
- PE (chest pain)
- Bronchiectasis (?)
- Obliterative bronchiolitis (suspect in elderly, ?)
Natural history
- Most children with asthma grow out of it in adolescence or suffer much as less as adults, but not all
- A significant number of people develop chronic asthma late in life (late-onset)
Clinical features which increase probability of asthma in adults
- Wheeze, SOB, chest tightness
- Diurnal variation
- Response to exercise, allergen, cold air
- Symptoms after aspiring or beta-blocker
- Personal history of atopy
- Family history of atopy/asthma
- Widespread wheeze on auscultation
- Unexplained low FEV1 or PEFR
- Unexplained blood eosinophilia
Disturbed sleep is a sign of severe asthma. What is a sign of poorly controlled asthma in atopic individuals?
High levels of eosinophils in the blood
Units for PEFR
L/min
Factors that influence PEFR and spirometry
Age, gender, height
